1. Field of the Invention
This invention relates to a semiconductor integrated circuit which performs phase synchronization, and more particularly to a semiconductor integrated circuit which is suitable for use in a magnetic disk system.
2. Description of the Related Art
In recent years, it has been made various attempts to reduce the number of circuit components and improve the performance and function by large-scale integration of electrical circuits.
Generally, in the functional section which deals with analog signals, it is advantageous that the circuit for dealing with analog signals comprises a bipolar transistor circuit in view of its precision and frequency band. However, of such an analog section, data signal circuits deal with high-frequency signals and hence require an amplifying circuit of very wide frequency band and high precision so that the amount of electrical power consumption would necessarily increase, thus making the integration difficult.
Thus regarding the functional section which deals with analog signals, it has been currently difficult to attain both the high performance and the high integration together. Consequently, in the conventional technology, the section which requires a high precision and a high frequency band was provided in the form of plurality LSI chips manufactured by bipolar processes.
For example, in the conventional magnetic disk system, semiconductor integration of a pulse shaping circuit dealing with analog signals, and of a phase synchronizing block dealing with digital signals analogously was realized as a plurality of LSI chips.
However, this conventional semiconductor integration would not reduce the number of component parts of the signal circuit block so that it would be difficult to realize reduction of the apparatus size and improvement of the performance.
Further, because of plural LSI chips, the amount of electrical power consumption of buffers for inputs/outputs of the LSI circuits was large. Signal lines between the LSI circuits were apt to interfere with each other via a substrate.
A solution of the problems was proposed by Japanese Patent Laid-Open Publication No. 274516/1989 which corresponds to U.S. application Ser. No. 07/392,552 for "Data separator and signal processing circuit". According to these applications, a part of a data separator is manufactured by a Bi-CMOS process, thereby the data separator could be included in one chip. However, a pulse generator could not be included in the same chip as the data separator was composed. Therefore, all the problems described above could not be solved.